Castle Crashers is one I definitely plan to download the demo for, I've heard good things and enjoyed Alien Hominid. Is it required to have games loaded onto the ps3? I always thought it was just an option to improve loading times. I don't own one so I don't personally know.

I don't have many PS3 games, but I think they've all required an install. Obviously it's not copying the entire disc to the hard drive, but I think they've been a couple gigs in size. The Xbox 360's upcoming install feature is optional and to improve loading times, though.

I believe it is due to the fact the BR disks read at a slower speed than a standard DVD... or so I have been told. To keep things running smooth you must install some of the game onto the hard drive.

In the case of metal gear solid 4, the game puts 4 gigs of stuff onto your HD.

But HOLY CRAP that game has amazing sound!!! I watched the opening cut scenes (all 45 minutes of them!) and I can honestly say that MGS4 has THE BEST surround sound out of any game I have ever played, and probably out of any movie I own as well.